Nicknamed ‘Planet Nine’, the idea first emerged in 2014 when Dr Scott Sheppard and Professor Chad Trujillo sought to explain a strange cluster of six small objects in the Kuiper Belt, a field of icy and rocky objects beyond Neptune.

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Their orbits all tilted in the same way, an arrangement that is nearly impossible to generate without the help of some external force.

Dr Sheppard and Prof Trujillo suggested a large planet was lurking in the shadows, warping the orbits of objects that came near.

Now the same team has found a similar body whose orbit is being similarly affected. At about 186 miles (300km) wide, it is on the small side of being a dwarf planet.

It is about 80 astronomical units (AU) from the sun, a measurement defined as the distance between the Earth and sun. For context, Pluto is around 34 AU.

A comparison of 2015 TG387 at 65 AU with the Solar System’s known planets (Picture: Carnegie Institution for Science)

Saturn can be seen at 10 AU and Earth is at 1 AU, as the measurement is defined as the distance between the sun and our home planet (Picture: Carnegie Institution for Science)

Called 2015 TG387, it has a very elongated orbit meaning it never comes close enough to the Solar System’s giant planets, like Neptune and Jupiter, to have significant gravitational interactions with them.

Dr Sheppard, of Carnegie Institution of Science, said: ‘These distant objects are like breadcrumbs leading us to Planet X.

‘The more of them we can find, the better we can understand the outer Solar System and the possible planet that we think is shaping their orbits – a discovery that would redefine our knowledge of the Solar System’s evolution.’

Prof Trujillo, of Northern Arizona University, ran computer simulations for different hypothetical Planet X orbits that explained how 2015 TG387 would actually be shepherded by its gravity.

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It never comes closer to the sun, a point called perihelion, than about 65 AU. Only two other objects, known as 2012 VP113 and Sedna at 80 and 76 AU respectively, have more-distant perihelia.

The orbits of the new extreme dwarf planet 2015 TG387 and its fellow Inner Oort Cloud objects 2012 VP113 and Sedna as compared with the rest of the Solar System (Picture: Carnegie Institution for Science)

The 2015 TG387 was nicknamed ‘The Goblin’ by the discoverers, as its provisional designation contains TG and the object was first seen near Halloween (Picture: Carnegie Institution for Science)

Dr Sheppard said: ‘These so-called Inner Oort Cloud objects like 2015 TG387, 2012 VP113, and Sedna are isolated from most of the Solar System’s known mass, which makes them immensely interesting.

Follow-up observations at the Magellan telescope at Carnegie’s Las Campanas Observatory in Chile and the Discovery Channel Telescope in Arizona were obtained in 2015, 2016, 2017 and 2018 to determine 2015 TG387’s orbit.

The location in the sky where 2015 TG387 reaches perihelion is similar to 2012 VP113, Sedna, and most other known extremely distant trans-Neptunian objects, suggesting that something is pushing them into similar types of orbits.

Its discovery was announced by the International Astronomical Union’s Minor Planet Centre in Washington DC. A paper describing it has also been submitted to the Astronomical Journal.